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Marine Ecology Progress Series

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MEPS - Vol. 368 - Feature article
Skeletons of top predators provide a record of long-term changes in ecosystem structure. Graphic: J. T. Christensen

Christensen JT, Richardson K


Stable isotope evidence of long-term changes in the North Sea food web structure


Several studies based on fisheries data indicate a relative decrease in the abundance of large fishes in the North Sea over the past century, and thus suggest that fundamental changes in pelagic ecosystem structure have occurred. However, fisheries data are available only for limited time periods, and they are influenced by fishers’ behaviour. Christensen & Richardson have analysed stable isotope (?15N and ?13C) abundances in harbour porpoise skeletons dated between 1848 and 2002. The results provide evidence of a change in North Sea ecosystem structure since the mid-20th century, as porpoises began feeding at lower trophic levels. This apparent change in ecosystem structure coincides with a period of intensification of commercial fisheries.


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